Patients with spinal cord injuries often develop urinary complications. A spastic urethral sphincter is usually symptomatic of a spinal cord injury due to loss of neural connections between the bladder and central nervous system. Instead of relaxing, the urethral sphincter contracts when the bladder contracts to prevent or at least interfere with the release of urine. This in turn can cause recurrent urinary tract infections with progression to pylelonephritis, stone disease and amyloidosis. Also, when the bladder becomes distended but cannot void the urine therein, this can result in autonomic dysreflexia which is a spike in the patient's blood pressure. Renal failure is a common cause of death in spinal cord injury patients.
Although various bladder management techniques have been available they have not been without their drawbacks. Efforts to relieve bladder spasticity have traditionally been surgical. The surgical procedure, known as an external urethral sphincterotomy, is irreversible but may not always be effective. In one recent study the sphincterotomy failure rate was 25%. Jorge L. Lockart, et al: Sphincterotomy Failure in Neurogenic Bladder Disease, J. of Urology, Vol. 135, pp. 86-89, 1986. This is a relatively major surgical procedure with concomitant risk of systemic infection, which many patients would rather not undergo.
Medications are unreliable and the side effects can be troublesome.
Long-term indwelling catheters are convenient, but can lead to chronic urinary tract infections. Periodic self-catherization is difficult for many patients, especially for those with poor hand function. Condom catheters keep patients dry, but do not treat detrusor-sphincter dyssynergia or dysreflexia, if present.
A need has thus arisen for a less invasive, reversible means of relieving bladder spasticity. Intramuscular injection of a toxin, such as botulinum, has been used heretofore to treat strabismus, blepharospasm and torticollis in the eye, face and neck muscles. Alan B. Scott, Botulinum Toxin Injection of Eye Muscles to Correct Strabismus, Tr. Am. Ophth. Soc., Vol. LXXIX, pp. 734-770 (1981). However, the technique described therein is designed for extraocular muscles, which can be readily accessed by the attending physician. Heretofore there has not been available a pharmacological technique for treating the problem of detrusor-sphincter dyssynergia in patients with spinal cord injuries.